A 45-year-old female presents to the EP lab with complaints of palpitations and the following 12 lead ECG that was recorded in the emergency room 2 weeks prior.
12 Lead ECG:
A 69-year-old male came into the EP lab for an SVT study. The following ECG was recorded, what do you observe?
Answer:
Delta Waves
Delta waves are an ECG finding that shows the presence of an accessory pathway. With a pathway that can conduct from A to V over the accessory pathway (AP), the ventricle is pre-excited and is referred to as WPW. Not all APs are able to conduct in this direction; therefore, delta waves are not always observed in patients with an accessory pathway.
Catheter Placement
Catheters were placed and the following measurements were acquired:
- PR: 125
- QRS: 125ms
- QT: 430ms
- AH: 110ms
- HV: 0ms
What observations can be made?
Answer:
The only abnormal measurement is the HV of 0 ms which is measured from the His to the earliest ventricular activation seen here on the surface QRS.
This demonstrates the ventricle was activated early as it was depolarizing (QRS) at the same time it exited the AV node (H). This is also seen on the surface ECG with the delta wave.
Also, note the AV fusion seen on CS 1,2 (left side of the heart).
(Ideally a large A will be seen on the His channel)
Catheter Repositioning
We have clear evidence of an accessory pathway on the left side of the heart. The earliest ventricular activation seen in the intracardiac electrograms is on CS distal.
This is just the earliest seen. It does not necessarily the earliest; therfore, the physician advanced the coronary sinus catheter to bracket the pathway location.
Baseline Testing
Next, baseline testing was performed.
Where are we pacing?
What type of pacing?
What is observed?
Answer:
Decremental ventricular pacing is occurring down to the rate of 250 ms (very fast for ventricular pacing)
Notice that each impulse captures the ventricle (wide QRS) and conducts to the atrium with the earliest signal on CS 3,4; although, CS 3,4 AV interval is not fused. Again, a placement of the His catheter with a larger A would be advisable but was not needed to make any of these determinations.
This shows that the AP can conduct in the retrograde direction from V to A over the pathway.
Baseline Testing Continued
Where are we pacing?
What is observed?
Answer:
Pacing is occuring via proximal CS at 600 ms (100 bpm).
Each atrial stimulus captured the atrium and conducted to the ventricle…. but how did it get to the ventricle?
It traveled through both the AV node as well as over the accessory pathway. Notice the very large delta way on the surface ECG. There is much more preexcitation seen as the proximal CS is closer to the AP than the sinus node. Therefore, the ventricle was able to deploarize even more before the normal wave of activation traveled through the AV node.
Ablation
For stable catheter positioning, as well as to see activation over the AP, the physician chose to ventricular pace throughout mapping and ablation. To map, we are searching for the earliest atrial activation to demonstrate the site that the AP cuts from the ventricle to the atrium (as well as watching for AP potentials).
VA fusion is observed at the successful site as seen here.
3D Map of ablation site
As you can see on the 3D map, the site of ablation is on the anter aspect of the lateral LA. Ideally we would like to bracket the mapping (later on each side of early); however, the physician liked this signal and desided to ablate.
This was observed within seconds of ablating….
What is our thoughts?
Answer:
Successful Ablation
Notice ventricular pacing no longer travels retrogradely up the AP at the end of the recording.
Post Ablation
Here is a final recording after AP ablation.
Notice that with sinus activation, the earliest atrial activation is seen on CS 1,2 rather than CS 9,10.
Is this normal?
What is happening?
Answer:
Normal Activation
This is normal activation BUT an abnormal CS placement.
Recall that the CS catheter was advanced at the beginning of the study to bracket the pathway. This causes the distal CS to be located on the more anterior aspect of the LA and the proximal in the mid posterior aspect unlike the normal CS ostium location.
So, CS 1,2 is recording the activation that occured over Bachmann’s bundle before it was able to reach the proximal CS.
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